Earth History

Page
6

(Effects of Reduction)

1% Reduction In O3 2% increase in UV-B

Skin sunburns, tans, Skin cancer

Absorbed by DNA DNA damage

Possible eye cataracts

Interferes with photosynthesis

Organisms in 1st 5metre of the Oceans at risk

( phytoplankton in particular )

Slide 43

Chlorofluorocarbons & Ozone

Destruction of the Ozone Layer discovered in 1970’s by CFC’s ( Chlorofluorocarbons)

First synthesized Swartz (1892)

Used as refrigerants 1928 (Midgely & Henne)

CCl4 + xHF CCl(4-x)Fx + HCl

(Aerosol Propellants & Air conditioners)

Slide 44

Ozone Protection

Protection

O2 + h 2O.

O. + O2 O3

O3 + h O. + O2

( UV-B)

Slide 45

Ozone Destruction

Destruction CFCl3 Cl. Chlorine

(UV-C, UV-B) Radical

Cl. + O3 O2 + ClO.

ClO. + O. Cl. + O2

ClO. + ClO. ClOOCl (relatively stable)

Slide 46

Control of CFC’s

CFC’s are now under strict control and their use has been curtailed.

Australia signed the international treaty.

“The Montreal Protocol“ in June 1988 which has a program controlling the use and reduction of CFC’s.

Slide 47

Uses of CFC’s

Compound Use

CFC- 11 CFCl3 Refrigeration, aerosol, foam

CFC-12 CF2Cl2 sterilization, cosmetics

food freezing, pressurized

blowers.

CFC-113 CCl3CF3 solvent, cosmetics

Halon 1301 CBrF3 fire fighting (discontinued)

Slide 48

Lifetime of CFC’s

Compound Ozone Depleting Lifetime(yrs) Potential

CFC- 11 1.0 65 -75

CFC-12 1.0 100 - 140

CFC-113 0.8 100 - 134

CFC-115 0.6 500

CCl4 1.2 50 - 69

Halon 1301 10 110

Slide 49

Naming of CFC’s

( 90 Rule)

CFC’s name is related to its Formula.

CFC 123 123 + 90 = 213

The remaining bonds are allocated to Cl or Br

C = 2 , H =1 , F = 3 , Cl = ( 8 - 6) = 2

CFC 123 is CF3CHCl2

Letters with the number indicate an isomer.

C

H

F

Slide 50

Chloromonoxide

Evidence for the destruction has been linked to the catalytically active Chloro monoxide ClO. & Ozone profiles as one goes South.

It is interesting to note how little Chloro monoxide effects the amounts of Ozone.

Slide 51

Relationship between ClO. & O3